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/*
* arch/arm/mach-tegra/localtimer.c
*
* Copyright (C) 2002 ARM Ltd.
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/clockchips.h>
#include <asm/irq.h>
#include <asm/smp_twd.h>
#include <asm/localtimer.h>
#ifdef CONFIG_USE_ARM_TWD_PRESCALER
#define CPU_FREQ_SCALE_SHIFT 24
#define CPU_FREQ_SCALE_DIVIDER (0x1 << CPU_FREQ_SCALE_SHIFT)
#define CPU_FREQ_SCALE_INIT 125
extern unsigned long twd_prescaler;
#endif
/*
* Setup the local clock events for a CPU.
*/
void __cpuinit local_timer_setup(struct clock_event_device *evt)
{
#ifdef CONFIG_USE_ARM_TWD_PRESCALER
if (!twd_prescaler) {
twd_prescaler = CPU_FREQ_SCALE_INIT - 1;
smp_wmb();
}
#endif
evt->irq = IRQ_LOCALTIMER;
twd_timer_setup(evt);
}
#ifdef CONFIG_USE_ARM_TWD_PRESCALER
/*
* Find new prescaler value for cpu frequency changes, so that local timer
* input frequency is kept at calibration level. Save new value in shadow
* variable - do not update h/w.
*/
void local_timer_rescale(unsigned long cpu_freq_khz)
{
static unsigned long cpu_freq_scale_mult = 0;
unsigned long scale;
/* 1st call at boot/calibration frequency */
if (cpu_freq_scale_mult == 0) {
cpu_freq_scale_mult = ((twd_prescaler + 1) <<
CPU_FREQ_SCALE_SHIFT) / cpu_freq_khz;
printk("Local timer scaling factor %lu, shift %d\n",
cpu_freq_scale_mult, CPU_FREQ_SCALE_SHIFT);
return;
}
scale = (unsigned long)((((uint64_t)cpu_freq_khz * cpu_freq_scale_mult)
+ CPU_FREQ_SCALE_DIVIDER -1) >> CPU_FREQ_SCALE_SHIFT);
twd_prescaler = scale - 1;
}
#endif
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